Oceanic Systems 3281 is a versatile water level sender designed for accurate measurement of fresh water tank levels. It offers two output modes: Level Mode for precise level indication and Volume Mode for volume calculation considering tank shape. Installation is straightforward, with a 1.25" BSP threaded mount and NMEA2000 interface. The device features a coated rod for reliable sensing, and self-calibration for empty and full tank levels using a magnet.
Oceanic Systems 3281 is a versatile water level sender designed for accurate measurement of fresh water tank levels. It offers two output modes: Level Mode for precise level indication and Volume Mode for volume calculation considering tank shape. Installation is straightforward, with a 1.25" BSP threaded mount and NMEA2000 interface. The device features a coated rod for reliable sensing, and self-calibration for empty and full tank levels using a magnet.
The Oceanis Systems’ 3281 NMEA2000® Fresh Water Level Sender measures the tank level or tank volume of the
vessels fresh water tanks.
It is very important that it is installed and set up correctly according to this manual. Please read and follow the
installation and setup instructions carefully to achieve the best results. (applicable for all variants)
The 3281 NMEA2000® Fresh Water Sender has the following features:
• Water level sensing from 250mm to 2 metres
• User settable for tank Level or tank Volume output
• User settable tank instance from 0 to 15
• Heartbeat blue LED to indicate normal activity
• Red Warning LED to indicate damaged rods.
• 1.25” BSP single threaded mount
• NMEA2000® Interface
Take great care when unpacking the sender that the coated rod is not damaged in any way. If the coating is
scraped or punctured the sender will not work.
We test every sender before it is packed so the coated rod is protected against transit damage. Do not remove the
protective packaging until you are ready to install the sender.
You should find the following items in the 3281 shipping tube:
1 x 3281 NMEA2000® Fresh Water Level Sender
1 x Water Sender Probe End Cap (May already be attached)
1 x 3281 User Manual (This document)
1x 30g tube of silicone, if unit is not already cut to length
1.1 MOUNTING LOCATION AND REQUIREMENTS
The sender is designed to be mounted on a flat area on the top of the water tank over the tank’s deepest part.
Examine the tank internal structure and choose a location that ensures the sender probes will not chafe on any of
the tank’s internal structure or baffles.
The sender requires a 1.25 inch standard BSP threaded mounting hole with a small 45° machine chamfer at the
top to seal against the sender mounting O ring.
If the tank has an existing SAE 5 bolt hole then the optional
3261 Mounting ring can be attached to the SAE 5 bolt holes to
provide a 1.25” BSP threaded hole mount for the Water Sender.
1.2 MEASURING SENDER LENGTH
The sender may be supplied already cut to length with the probe end cap already installed and be ready to install
into the tank if you have supplied the required cut length at the point of ordering. In this case there is no extra
work to do in this part.
If the sender was supplied in a standard length to be cut down then the finished length should be determined by
measuring as shown in the diagram.
INSTALLATION
1
Magnet Area
Make certain sender and water
pickup are at the same level.
Water tank/container
Tank No.
Red LED Indicator
Blue LED Indicator
Optional 3261 Mounting Ring.
Finished Length
25mm / 1” between the
end of the sender and
the bottom of the tank
25mm / 1”
Measure from
the underside of the
Water Sender
FRESH WATER LEVEL SENDER
Part Numbers: 3281
INSTALLATION AND OPERATING INSTRUCTIONS
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Cut the coated and uncoated rod to length using a sharp hacksaw.
CAUTION
BE VERY CAREFUL NOT TO DAMAGE THE PLASTIC COATING ON THE REMAINING LENGTH OF ROD DURING THE
CUTTING PROCESS. IF YOU ARE SUPPORTING THE ROD DURING THE CUTTING PROCESS SUPPORT THE ROD ON THE
PART BEING REMOVED. IF THE PLASTIC COATING IS DAMAGED THE SENDER WILL NOT WORK!
After cutting the rods to length remove any sharp edges with a file. The cut end now needs to be insulated by
means of the clear plastic end cap included with the unit. Enter the insulated rod in the enclosed part of the end
cap and the plain rod in the other end as shown in this image.
Fill the clear plastic end cap with silicone sealant before pushing insulated rod onto the cap.
Push the insulated rod firmly into the enclosed end until it is fully home as shown the following image. This will
be quite stiff and care must be taken not to damage the coated rod in this operation.
Carefully insert the Water Sender probe into the threaded hole in the top of the tank. Ensure that the probe
coating does NOT scrape against the edge of the tank. Tighten sender sufficiently to prevent leaks.
1.5 CONNECTING THE NMEA2000® INTERFACE
The unit must be connected with POWER OFF to prevent damage.
The NMEA2000® interface cable on the unit should be connected to a nearby NMEA2000® Tee connector (part
number 3802). The male end of the cable should be inserted into the female Tee connection noting the position of
the keyway in the plug and the socket. This cable can be extended up to a maximum length of 6 metres to the Tee
connector. Ensure that the locking ring is securely tightened so that the connection is waterproof and secure.
1.3 CUTTING TO LENGTH 1.4 INSERTING SENDER INTO THE TANK
To display
3804 Male
Terminator
3802 T - Adaptor
+12v
3281 Water Sender
250-3000mm
NMEA2000® Network Backbone
Support both ends of
Water Sender
Make sure the Plastic outer is well past the
O-rings to ensure a good seal.
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2.3 SETTING THE OUTPUT MODE
The 3281 Fresh Water Sender has two output modes to choose from. Level Mode or Volume Mode.
LEVEL MODE is when the sender outputs from 0 – 100%. It indicates the exact LEVEL of the fluid in the tank. The
user can tell when the unit is in Level Mode because the blue LED flashes ONCE every 2.5 seconds when a level
message has been sent.
VOLUME MODE is when the sender outputs from 0-100% but reflects the actual fluid volume within the tank taking
allowance for the tanks internal shape. The user can tell when the unit is in Volume Mode because the blue LED
flashes twice rapidly every 2.5 seconds when a volume message has been sent.
The Volume Mode PGN message is exactly the same as the Level Mode PGN message which means that the volume
can easily be shown on any NMEA2000® display that accepts Fluid Level PGNs from tank senders. The Volume
Mode Tank data can be entered from any Oceanic Systems Display that is equipped to set up this data. Please
contact us for more information on these displays. It can also be set up at manufacture if the information is made
available at the time of ordering.
SETTING LEVEL MODE
Level Mode can be set by setting the “Tank No.” switch to “C” and then placing a small magnet on the “Magnet
Calibration” position on the label. The blue LED will flash for 2 seconds to indicate that the unit saw the magnet.
Then return the “Tank No.” switch to it’s original position and the sender will transmit Level messages as
indicated by the blue LED flashing ONCE briefly every 2.5 seconds.
SETTING VOLUME MODE
Volume Mode can be set by setting the “Tank No.” switch to “D”, then placing the magnet on the “Magnet
Calibration” position on the label. The blue LED will flash for 2 seconds to indicate that the unit saw the magnet.
When the switch is returned to it’s original positions the sender will transmit Volume messages as indicated by the
blue LED flashing rapidly TWICE every 2.5 seconds.
If the senders Volume Mode Tank Data has NOT been set up, and the unit is accidentally set to Volume Mode, the
data transmitted will actually be the Level Data. This means the unit will remain fully functional.
2.1 TANK CONFIGURATION
To configure the sender to measure the fluid in the tank, make curtain that the ‘Tank Type’ rotary dial is set to
position 1.
Please note that the contents of waste and black water tanks can coat the probes and cause misreadings. If this
occurs then carefully wipe down the probes with a soft cloth and fresh water.
We do not recommend this sender for waste or black water tanks. Please contact [email protected] for
recommended solution.
2.2 TANK DEVICE INSTANCE
NMEA2000® requires a unique Device Instance to be set for each 3281 NMEA2000® Fresh Water Sender on a single
network. This is settable from device instance 0 to Device Instance 15 using the right hand small rotary switch on
the top of the sender labeled “Tank No.”
This means that each Fresh Water tank should have a device instance starting from 0. The Instance can be set at
any time regardless if power is on or off. The switch counts from 0 – 9 then A – F being equivalent to Device
Instance 0 – 15.
The NMEA2000® Device Instance is set by using the small rotary switch on the front panel labeled “Tank No.” as
per the following table:
CONFIGURATION
2
Tank Type
Fresh Water
Switch Position
1
Switch Position
0
Device Instance
0
1
2
1
2
3
4
3
4
5
6
5
6
7
8
7
8
9
A
9
10
B
C
11
12
D
E
13
14
F 15
2
5
Waste Water
Black Water
0
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
Tank No. set to ‘C’ Set level mode with a Magnet
Blue LED flashes
for 2 seconds
0
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
Tank No. set to ‘D’ Set Volume mode with a Magnet
Blue LED flashes
for 2 seconds
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The following table will help diagnose common faults:
MAINTENANCE
Ensure that the sender is mounted securely in the top of the tank and that there are no liquid leaks. Reset and
tighten if necessary. Check the security of the NMEA2000® cable to the NMEA2000® Tee Connector and tighten if
necessary. Clean the unit with a soft cloth. Do not use chemical cleaners as they may remove label markings. The
probes should be cleaned with plenty of water and a soft rag. Be very careful not to damage the coated rod whilst
cleaning.
3
SETTING TANK EMPTY TANK FULL CALIBRATION
Copyright © 2020 Oceanic Systems (UK) Ltd. All rights reserved. Our policy is one of continuous product improvement so product
specifications are subject to change without notice. Oceanic Systems products are designed to be accurate and reliable. However,
they should be used only as aids to vessel monitoring, and not as a replacement for traditional navigation and vessel monitoring
techniques. NMEA2000® is a registered trademark of the National Marine Electronics Association.
Oceanic Systems (UK) Ltd
Unit 10 -11 Milton Business Centre, Wick Drive,
New Milton, Hampshire, BH25 6RH, United Kingdom
Tel (UK): +44(0)1425 610022 Tel (USA): (844)898 6462
Fax: +44(0)1425 614794 Email: [email protected]
Web: www.osukl.com
DOC NO. 00002 Rev. G v5
When the unit is first installed it needs to be calibrated to the tank. This is easily done as follows:
3.1 TANK EMPTY CALIBRATION
When the unit is first installed in an EMPTY tank and powered on the Tank Empty Calibration is done by setting the
“Tank No.” switch to “E” then placing a small magnet on the “Magnet Calibration” position on the label. The blue
LED will light for 2 seconds to indicate that the unit saw the magnet and that the empty calibration is complete.
3.2 TANK FULL CALIBRATION
The Tank Full Calibration is easily done in a FULL tank and powered on by setting the “Tank No.” switch to “F”.
Then place a small magnet on the “Magnet Calibration” position on the label to set the Full Calibration position.
The blue LED will light for 2 seconds to indicate that the sender saw the magnet and that the full calibration point
has been set.
In all cases do not forget to set the “Tank No. switch back to it’s original tank number.
LED on for about 2 seconds
LED Flashes twice every 2.5 seconds
LED flashes once every 2.5 seconds
LED flashes rapidly
LED does not flash
Calibration magnet detected
Inaccurate Reading
Check end cap still installed on end of sender,
carefully clean the sender rods and recalibrate
using instructions above.
Red LED on or red LED flashing intermittently While a short is detected due to an ill fitting end cap
or damaged sleeve the red LED will be on.
Normal Operation in Volume mode (see 2.3 above)
Normal Operation in Level mode (see 2.3 above)
Network not terminated correctly or no other
NMEA2000® device on the network
Check power on network or Tank Type switch
not set to valid value
TROUBLESHOOTING
4
0
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
Tank No. set to ‘E’
Empty Tank
Empty Tank
Full Tank
Full Tank
Set empty level with a Magnet
Blue LED stays on
for 2 seconds
Do not touch the metal
casing of the device
during calibration.
0
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
Tank No. set to ‘F’ Set full level with a Magnet
Blue LED stays on
for 2 seconds
Do not touch the metal
casing of the device
during calibration.
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2
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Oceanic Systems 3281 is a versatile water level sender designed for accurate measurement of fresh water tank levels. It offers two output modes: Level Mode for precise level indication and Volume Mode for volume calculation considering tank shape. Installation is straightforward, with a 1.25" BSP threaded mount and NMEA2000 interface. The device features a coated rod for reliable sensing, and self-calibration for empty and full tank levels using a magnet.
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